Current Launch vehicles and upper stages must only keep their fuels for minutes or hours, so they are only insulated to keep boiloff to a few % per day - I've seen 21% per day quoted for Centaur on coasts to GEO.
For proposed "fuel depots" or Mars missions, hydrogen (and oxygen) must be kept liquid for years with minimal losses, is this achievable purely with insulation and sun shading or are refrigeration methods being considered?